Manganese Blue Hue vs Sky Blue

How close are they?

ΔE 23.4, loose: different enough that you should pick on purpose. Sky Blue is a little lighter, much more muted than Manganese Blue Hue.

Can I use Sky Blue instead of Manganese Blue Hue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Sky Blue is a little lighter, much more muted than Manganese Blue Hue.

Can I use Manganese Blue Hue instead of Sky Blue?

The same difference applies the other way round: Manganese Blue Hue is a little darker, much more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.